Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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385 FXUS66 KPDT 031101 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 401 AM PDT Wed Jul 3 2024 .SHORT TERM...Today through Thursday...A dry northwesterly flow will remain with a ridge of high pressure offshore of the region. Wind gusts (20-30 mph) will occur along the Columbia River Gorge and Kittitas valley now through early this morning. Wind conditions should decrease to light around 10 mph or less starting Wednesday afternoon hours (80-100% confidence). Otherwise, the overall pattern and conditions will be constant with persistent conditions for temperatures and winds. As the ridge continues over PacNW, starting Thursday will be the beginning of a long hot dry period into next week. High temperatures will increase to the lower to mid 90s across the lower elevations and 80s in the mountains. Few clouds could pass by but overall clear skies throughout this period, providing easy viewing of evening firework displays for Independence Day. Dry conditions will persist with low relative humidity in the teens to lower 20s. Feaster/97 .LONG TERM...Thursday night through Wednesday...A period of very unusually hot temperatures and warm overnight lows is the main sensible weather concern. Highs approaching 20 degrees above normal will reign beginning Friday and prevail into early next week. Meantime, lows will be 10-15 degrees above seasonable normals. The combination of daytime highs with limited relief overnight will promote an increased risk of heat-related impacts with Major (category 3) to locally Extreme (Category 4) HeatRisk, notably across the lower elevations of the Lower Columbia Basin, south central WA, eastern Gorge, and north central OR into the foothills of the Blues. An Excessive Heat Warning was issued starting Friday through Tuesday, though there is some uncertainty with the duration of the heat event with potential to extend it possibly. The limited relief overnight there will enhance the heat wave. Of note, Tri-Cities are forecast to hit or exceed 105 F five times in a row starting Saturday (to Wednesday) which would tie for first for the number of consecutive days greater than or equal to 105 F. Hot conditions extend into central Oregon and the John Day Basin, however, modest overnight relief is expected at this time thus a Heat Advisory was issued Friday-Tuesday. This stems from low temperatures being cooler and contributing less to the overall heat stress. Mountains will see warmer than normal temperatures too, but the level of heat will affect mostly those heat- sensitive or without cooling/hydration with more adequate relief overnight. Ensemble guidance is in good agreement with the large scale pattern starting Thursday night with an upper-level ridge expected to be just offshore the West Coast and anticyclonic flow dominating. ECMWF ensemble mean 500 mb height forecasts at the center of the upper high continue to fall outside climo Thursday night. Little movement in the upper ridge anticipated by Sunday with it then over the West Coast with mean 500 mb heights forecast to still exceed the 99.5th percentile. Guidance shows the upper ridge then evolves eastward Monday and Tuesday with the upper ridge more over the Northern Intermountain West by the latter day. Limited differences in guidance that affect our sensible weather this weekend through Monday based on clustering scenarios with very unusually highs forecast. This is supported by increasing ECMWF EFI for MaxT over the weekend through Tuesday with the Sunday-Tuesday looking to hold the hottest temperatures in the lower elevations/Lower Basin (EFI values of 0.7-0.9). Of note, clustering highlights a potential open wave disturbance that could knock down highs (~20%) Tuesday. However, much of the synoptic outcomes favor a prolonged heat wave with continued support for heat extending to Wednesday (confidence 70-80%). && .AVIATION...12Z TAFS...VFR conditions with clear skies throughout the day. Gusty northwesterly winds will arrive for KDLS around 25 kts early afternoon before decreasing tonight (high confidence). Elsewhere, winds at other terminals will be 10 kts or less. Feaster/97 && .PRELIMINARY POINT TEMPS/POPS... PDT 83 54 90 55 / 0 0 0 0 ALW 87 57 93 57 / 0 0 0 0 PSC 90 58 95 60 / 0 0 0 0 YKM 89 54 94 56 / 0 0 0 0 HRI 89 56 95 57 / 0 0 0 0 ELN 86 56 92 56 / 0 0 0 0 RDM 85 48 92 51 / 0 0 0 0 LGD 80 51 87 52 / 0 0 0 0 GCD 83 50 91 52 / 0 0 0 0 DLS 88 59 97 64 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Excessive Heat Warning from noon Friday to 10 PM PDT Tuesday for ORZ041-044-507-508-510. Heat Advisory from noon Friday to 10 PM PDT Tuesday for ORZ505- 511. WA...Excessive Heat Warning from noon Friday to 10 PM PDT Tuesday for WAZ024-026>029-521. && $$ SHORT TERM...97 LONG TERM....80 AVIATION...97